Induction Motor Vibration Experience Lou Trahan DuPont at Sabine River Works, TX - Ethylene Unit Share our experience with rework of 5600 H.p. /1800 RPM motor during major TA
Background •Purge Propylene Refrigeration Compressor, Elliott 38M-6 driven by a Westinghouse 5600 Hp/ 1800 RPM induction motor with speed increaser to 3600 RPM
$Before the Turn Around$
Background Review • No indications of problems with this motor/system •Opportune time - Turn Around (Spring 2003) Preventative Maintenance
Vibration Signature Before T/A
Shop Work - Specifications •Remove the rotor •Clean the components •Inspect the rotor and stator •Inspect seals and bearings •Reassemble •Shop test •Ship
Problem Statement Re-installed motor at end of the TA Vibration is now unacceptable The frequency was from 1X to 7X Over 2.5 mils peak to peak (prior to rework - 0.65)
Vibration After the Overhaul
Vibration vs. Ambient Temp
Troubleshooting Vendor/consultants performed field inspection of the installation Continued for a month until… Unit S/D due to power outage Pulled motor Ran various shop tests for 1 week no conclusion
Shop Rework Couldn’t repeat the field results Pulled rotor out again Found hot spot with thermography in rotor, tightened loosened bar (not done in original rework) Balance checked on rotor - OK Stator core test - OK Performed bore sweep – OK Bearings - OK
Shop rework (cont.) Plastigaged the crush on the bearings, both were loose 0.001”- 0.003” Installed the seals with zero clearance, vendor recommends they will “RUN-IN” Continued monitoring vibration with motor vendor equipment and third party consultants
Vibration vs. Temp After Rebore Seals
Conclusion •Good sound rotating equipment practices are critical to performance •Detailed specifications are necessary •Simple issues like these seals are critical •Housing would shrink enough during ambient cooling to cause seal interference to worsen
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